An Investigation of the Usefulness, the Acceptability and Impact on Lifestyle of Alcohol Ignition Interlocks in Drink-Driving Offenders

  • Published: Department for Transport, Road Safety Research Report No. 88, 2008
  • Authors: D. Beirness, A. Clayton, and W. Vanlaar
  • Date Added: 28 Mar 2013
  • Last Update: 28 Mar 2013
  • Format: pdf


To examine the practicalities of setting up an alcohol ignition interlock programme in Great Britain, and assess the impact of the interlock on drink drive offenders and their families.


Longitudinal randomised control design, including interviews and focus groups. N=89 participants were included in the interlock programme. Trial participants had served a period of disqualification, had completed a Drink Drive Rehabilitation course, and were fully re-licensed.

Key Findings:

  • Participants reflected the typical demographic characteristics of drink driving offender populations.

  • Of the original 89 interlock participants, 39 (43 per cent) failed to complete the full 12 months. Twelve percent of the control group withdrew from the project early.

  • Over 90 per cent of the key events recorded by the interlock were stationary fails. Most participants (66 per cent) had fewer than three stationary fails per month. There were 328 recorded blood alcohol concentrations (BACs) over 80 mg/100 ml, corresponding to 172 potential drink driving trips.

  • The main issues reported by participants included being over the interlock limit the morning after drinking, delay in starting the car due to the time taken for the interlock to warm-up, and difficulties with rolling re-tests during a journey.

  • Despite the difficulties, there appeared to be greater acceptance of the interlock and a growing recognition of its value as the study progressed. Many indicated that it made them at least think seriously about their drinking, if not help change their drinking patterns outright. In total, 54 per cent of interlock participants reported consuming less alcohol at month 18 than at the beginning of the study, compared with 40 per cent of control participants. The difference between the two groups, however, was not statistically significant.

  • Given that the interlock was not used in a judicial setting, the findings may be different from those obtained when interlock use is mandated and/or participants must pay for the interlock themselves.


Alcohol ignition interlocks, longitudinal research.


Evaluation conducted within Great Britain.